1. Field of the Invention
Aspects of the present invention relate to a microactuator, which reflects light to change a light path.
2. Description of the Related Art
In recent years, the development of printers and other image forming apparatuses has been oriented toward increasing printing speed. In order to design high-speed printers, it is necessary to accelerate the operations of a polygon mirror, since the operation of the polygon mirror significantly affect the printing speed of the printers. However, since a spindle motor, which is required for driving most polygon mirrors, operates presently at a limited speed due to restrictions of oscillation, noise, and bearings, the speed of the polygon mirrors is limited to about 40,000 rpm (about 28 ppm) or lower. Accordingly, a new apparatus that can replace the spindle motor and the polygon mirror is required for ever-increasing the printing speed of printers.
In order to replace the spindle motor and the polygon mirror, a micro-electro-mechanical system (MEMS) microactuator has been developed. MEMS microactuators, most of which are hinged structures, are inexpensive and have good performance. However, a better performance is required for such microactuators to fulfill recent requirements for high speed and large displacement. It is difficult for the microactuators to meet both high-speed and large-displacement demands.
U.S. Pat. No. 6,956,684, which has been assigned to Texas Instruments Inc., discloses a hinged device that operates due to rotary power generated by an electromagnetic force, wherein a magnet is attached to a rotation body and a fixing body that excites the rotation body and has a bobbing coil. U.S. Pat. No. 6,956,684 discloses a method of attaching a magnet to a front side of an attaching member of a hinge layer and bonding a back layer having a compensation mass moment to a back side of the attaching member of the hinge layer such that the center of mass of the combined front and back layers is substantially coplanar with an axis of rotation of the hinged device in order to stabilize a scan operation. Furthermore, the attaching member and a back portion of the front layer define a spine structure, which allows reduction of weight and mass of the hinged device while maintaining the stiffness of the rotation body.
However, the mass of the rotation body is increased by use of the back layer having the compensation mass moment. Although the spine structure has been proposed to overcome this problem, the size (especially the height) of the entire rotation body is still increased. Also, since many components are used, the manufacture of the disclosed hinged device is difficult and costly.
As another example, U.S. Patent Publication No. 2005/0225821, which has been published by Texas Instruments Inc., discloses a hinged device having an optical surface. To allow balancing of the hinged device so that the center of mass of the hinged device is on the pivoting axis, a recess is formed in the optical surface instead of adding a back layer having a compensation mass moment. Here, since a hinge portion has the same thickness as the entire structure, controlling a resonance frequency and induced stress is difficult to achieve.